This invention relates to a novel offshore platform operable for use in the Arctic. More specifically, the invention relates to an offshore platform which may be used in Arctic locations where prolonged ice conditions may be encountered.
In the past, offshore platforms or towers have been extensively utilized around and upon the continental shelf regions of the world. Examples of offshore platform installations include supports for radar stations, light beacons, scientific and exploration laboratories, chemical plants, power generating plants, etc. Principally, however, offshore platforms have been used by the oil and gas industry in connection with oil and gas drilling, production and/or distribution operations.
In the initial stages of offshore drilling/production activity, operations were conducted along the near shore portions of the Gulf of Mexico in swamp or marshlands and seaward to water depths of 100 or more feet. In an attempt to keep pace with a burgeoning worldwide energy demand, more recent offshore activity has been decidedly more aggressive and has been directed to deeper water locations ranging up to 1,000 or more feet in depth and in areas of adverse environmental loading such as the unpredictable aerodynamics and hydrodynamic forces of the North Sea. Additionally, recent attention has become directed to the extremely adverse environment of the Arctic. In this connection offshore platforms operating in Arctic regions must be capable of working for prolonged periods on station while accommodating ice floes which would facilely topple and/or crush conventional open water platform designs.
In an attempt to cope with the Arctic frontier, numerous platform designs have been at least theorized by the offshore industry. Many arctic designs attempt to prevent massive ice floes from directly loading an offshore platform. More specifically, such designs rely primarily upon mechanical elements to break up advancing sea ice and/or melt the ice at a rate greater than the rate of advancement of the ice toward the stationary platform. Although such prior designs may provide a degree of theoretical appeal, the size and strength requirements of mechanical units and the heat energy required to implement ice melting concepts has tended to chill optimism for practical implementation of most previously known designs.
A significant advance was disclosed to the industry by the issuance of a United States Reusswig et al. U.S. Pat. No. 4,080,798 entitled "Arctic Drilling Base", of common assignment with the instant application. In this connection the Reusswig et al. patent discloses a drilling and/or production base wherein the lateral skin of the base is heated sufficiently to maintain a film of water between its sloping side wall surfaces and an advancing sheet of sea ice. This water film facilitates sliding action of the ice upwardly against the inclined side walls of the base to fail the oncoming ice in bending, rather than in compression.
Notwithstanding the advantages provided by the foregoing Reusswig et al. design, room for improvement remains. In this regard it would be highly desirable to provide an offshore platform for work in Arctic regions which would retain the advantages of preventing ice adhesion to a hull and failing the ice in bending while enhancing the capability of the platform to perform year round offshore operations. Additionally, it would be desirable to provide an offshore platform for work in the adverse conditions of the Arctic which would be structurally rugged while minimizing the weight of the platform. Further, it would be advantageous to provide an arctic offshore platform which would have a minimum draft to facilitate placement of the platform along near shore portions of the Arctic seas. Still further it would be desirable to provide an Arctic offshore platform wherein environmental hydrodynamic and ice forces may be effectively isolated from operational equipment mounted upon the platform. Yet further it would be advantageous to provide an Arctic offshore platform wherein supply and emergency abandonment of the platform may be enhanced.
The difficulties suggested in the preceding with regard to prior Arctic offshore platforms are not intended to be exhaustive, but rather are among many which may tend to limit the effectiveness and satisfaction with prior platform systems. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that prior Arctic offshore platforms will admit to worthwhile improvement.